What Sumit said, or you can also select it by hand using the lasso -tool. You might still need to do some cleaning around the edges especially if your photo has small resolution.
I use Gimp, it's free and it's similar to Photoshop, but I find Photoshop more versatile. Too bad it's so expensive. You can do a lot with Gimp too and there are some great tutorials out there to find the right features.